The closest known instrument to which this invention pertains is the slitless spectrometer. A typical slitless spectrometer consists of an astronomical, two mirror telescope with a plane grating placed between the secondary mirror and the photographic plate. When a star field is photographed, the images on the plate are the spectrum of each star placed at the position of the star. In this manner information is obtained on both the spatial location and the wavelength of many sources in the field simultaneously.
The detector array of a conventional imaging spectrometer in the diffracted order of the grating must provide M.times.N.times.W pixels (picture elements) where M.times.N is the number of spatial resolution elements in the two dimensional scene and W is the number of spectral resolution elements. For a system to provide a two dimensional field of view with both modest spatial resolution and wavelength resolution, this product, M.times.N.times.W, becomes prohibitively large.